Probing the Cytotoxicity of Semiconductor Quantum Dots

Abstract

With their bright, photostable fluorescence, semiconductor quantum dots show promise as alternatives to organic dyes for biological labeling. Questions about their potential cytotoxicity, however, remain unanswered. While cytotoxicity of bulk cadmium selenide (CdSe) is well documented, a number of groups have suggested that CdSe QDs are cytocompatible, at least with some immortalized cell lines. Using primary hepatocytes as a liver model, we found that CdSe-core QDs were indeed acutely toxic under certain conditions. Specifically, we found that the cytotoxicity of QDs was modulated by processing parameters during synthesis, exposure to ultraviolet light, and surface coatings. Our data further suggests that cytotoxicity correlates with the liberation of free Cd ions due to deterioration of the CdSe lattice. When appropriately coated, CdSe-core QDs can be rendered non-toxic and used to track cell migration and reorganization . Our results inform design criteria for the use of QDs in vitro and especially in vivo where deterioration over time may occur.

Silica-Coated CdTe Quantum Dots Functionalized with Thiols for Bioconjugation to IgG Proteins

“…Importantly, recent findings of acute toxicity in hepatocytes by CdSe without surface coatings highlights the need to properly condition the surface to be biocompatible and nontoxic. 16 Silanization of various metal and semiconductor nanoparticle systems have shown great success in protecting their surface characteristics. Liz-Marzan et al have grown a silica shell onto gold nanoparticles with controlled growth by initially priming the gold surface with (3-aminopropyl)-trimethoxysilane (APS) and growing the shell in ethanol using a modified Stöber method.…”

Aqueous phase synthesis of CdTe quantum dots for biophotonics

“…However, their toxicity in biological environments has not been fully understood [105]. Many groups are currently investigating the toxicity of cadmium-based QDs in vitro and in vivo [106][107][108][109].…”

Semiconductor nanocrystals for biological imaging

“…With continuous efforts in developing high quality biocompatible QDs, nanoparticles conjugated to antibodies, peptides and DNA have been prepared and targeted to cells and tissues specifically, allowing multiplexed labeling and long term studies that can not be achieved by using standard dyes [22][23][24][25][26][27][28][29]. Although QDs and organic dyes can have comparable quantum yields, the larger absorption cross-section of the nanocrystal results in a much stronger photoluminescence signal.…”